New blood test can tell bacterial from viral respiratory infections

A new test could help doctors correctly tell whether a patient's flu-like symptoms of respiratory infection are viral or bacterial in origin, helping to avoid the overprescription of antibiotics in situations where they're not needed.

Gene expression in the blood changes when the immune system is fighting off a bacterial or viral infection. Researchers at Duke University in North Carolina, USA, have identified a group of host gene expression patterns which can identify with 87 percent accuracy whether a respiratory infection is bacterial or viral, and infection or noninfectious.

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In a paper published in Science Transitional Medicine, Chris Woods and his colleagues describe how, by looking at blood samples from 273 subjects who presented at hospital with "community-onset acute respiratory infection or noninfectious illness", they were able to develop classifiers to identify the cause of the symptoms.

The accuracy of the new technique improves on the 78 percent accuracy of procalcitonin hormone levels as a marker of bacterial respiratory infections and on the 78 to 83 percent accuracy of three existing genetic classifiers.

The authors write that "these findings create an opportunity to develop and use host gene expression classifiers as diagnostic platforms to combat inappropriate antibiotic use and emerging antibiotic resistance."

The only downside to the technique is that the test currently requires up to ten hours of lab analysis to reach a result. Woods told New Scientist that his team is currently trying to adapt the test into a version that clinics could use get results within an hour.

Increasing levels of antibiotic resistance are linked to overprescription, among other factors, and recent findings show that, in the UK, such overprescription peaks during winter cold-and-flu season, particularly in deprived areas.